(1) Field of the Invention
The present invention relates to a process for producing polyethylene extruded foams.
(2) Description of the Prior Art
Polyethylene extruded foams have been widely used in various applications as a buffer, a heat-insulating material, packaging material, a building material, etc. Particularly, thin sheet-like extruded foams of this type are made by extruding a starting material with the clearance of a die lip being narrowed, and drawing the foam sheet at a drawing rate increased relative to a extrusion rate into a thin shape. Foams made by the extrusion foaming of low density polyethylenes (having a long chain-branched skeleton, which will be referred to as a LDPE hereinbelow), which have been widely used in recent years for reasons of an excellent foaming formability and softness, however, are accompanied by disadvantages. Because they have a small elongation and an inferior tensile strength, they are apt to break when being drawn into a thin shape. Therefore, it is difficult to produce a long and thin sheet-like extruded foam.